Abstract

Background:
Kappa-casein (κ-casein) gene polymorphism is a potential genetic marker that may influence production traits in livestock, yet its specific impact on the post-natal development of Awassi sheep offspring requires further validation.

Aim:
This study aimed to evaluate the effects of maternal κ-casein gene polymorphisms on the growth performance and morphometric body measurements of Awassi lambs, to evaluate genetic markers associated with offspring performance and provide insights for potential breeding selection strategies.

Methods:
A total of 53 Awassi sheep, comprising 24 mature ewes and 29 of their male lambs, were evaluated from January to July 2025. Lambs were allocated to four groups based on maternal κ-casein genotypes, determined by nucleotide sequencing of a 416 bp amplified fragment. Growth traits (birth weight, weaning weight, and body weight gain) and morphometric measurements (height at withers, heart girth, and diagonal body length) were analyzed using One-Way ANOVA. Although limited by small and unbalanced genotype sample sizes, preliminary parametric structures were verified.

Results:
Group 1 was the predominant genotype, accounting for 50% of the flock distribution (P ≤ 0.05). No significant differences were observed in birth weights among the four groups, suggesting that maternal κ-casein variations may not exhibit a detectable association with initial birth weight. However, Group 3 displayed lower weaning weight (20.5 kg), total weight gain (16.55 kg), and daily weight gain (0.276 kg) compared to the other groups (P ≤ 0.05). No significant differences were found among Groups 1, 2, and 4. Morphometric assessments revealed significant differences (P ≤ 0.05) between Group 1 and Group 3 in body height, heart girth, and body length, while no significant differences were found between Groups 2 and 4.

Conclusion:
Maternal κ-casein polymorphism shows potential preliminary associations with pre-weaning growth; however, due to small and unequal genotype group sizes, these findings require cautious interpretation. Selecting lambs from Group 1 dams may be tentatively recommended for rapid fattening systems, while Group 3 progeny may require further multi-generational evaluation due to lower observed growth and structural parameters.

Key words: Awassi lambs; Genetic polymorphism; Growth traits; Kappa-casein; Morphometric measurements.